Mr. Lizard appeared on Dinosaurs as a parody of the television show Watch Mr. Wizard, whose host helpfully taught generations of children about science. Mr. Lizard's show, Ask Mr. Lizard, was vaguely related to scientific principles, but mostly existed as a way of ridding the world of young dinosaurs named Timmy. After the often violent death of his assistant, Mr. Lizard would cheerfully call off camera, "We're going to need another Timmy!"
Mr. Lizard first appeared in "The Golden Child", where he was voiced by Bill Barretta.